导入语句前面的下划线是什么意思? [英] What does an underscore in front of an import statement mean?

问题描述

我看到了这个例子来自sqlite3 在 GitHub 上:

I saw this example from sqlite3 on GitHub :

import (
        "database/sql"
        "fmt"
        _ "github.com/mattn/go-sqlite3"
        "log"
        "os"
)

并且似乎无法找到 import 语句前面的下划线是什么意思.

and cannot seem to find what the underscore in front of an import statement means.

推荐答案

简答:

它用于导入一个包，只是为了它的副作用.

Short answer:

It's for importing a package solely for its side-effects.

来自 Go 规范:

要仅为其副作用(初始化)导入包，请使用空白标识符作为显式包名称:

To import a package solely for its side-effects (initialization), use the blank identifier as explicit package name:

导入_lib/数学"

在 sqlite3 中

对于 go-sqlite3，下划线import 用于在 init() 函数中将 sqlite3 驱动注册为数据库驱动的副作用，不导入任何其他函数:

In sqlite3

In the case of go-sqlite3, the underscore import is used for the side-effect of registering the sqlite3 driver as a database driver in the init() function, without importing any other functions:

sql.Register("sqlite3", &SQLiteDriver{})

一旦以这种方式注册，sqlite3 就可以在您的代码中与标准库的 sql 接口一起使用，如示例所示:

Once it's registered in this way, sqlite3 can be used with the standard library's sql interface in your code like in the example:

db, err := sql.Open("sqlite3", "./foo.db")

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